It is known to provide a vortex generator capable of creating a vortex of fluid flowing therethrough. For instance, it is known to provide an intake vortex generator in a vehicle air intake system for creating a vortex of intake air flowing into a combustion chamber of an internal combustion engine (e.g., when the engine is started or when the engine idles) to improve combustion efficiency and reduce fuel consumption and the like. (See, e.g., JP-A-2003-293775, pages 1-5, FIGS. 1 to 6.) Such an intake vortex generator is provided with a housing 102 and a flow control valve 105 as shown in FIGS. 7, 8A and 8B. The housing 102 constitutes an intake manifold for the intake of air into a combustion chamber 101 of the internal combustion engine. The intake flow control valve 105 has a valve shaft 103 constituting the center of rotation and that rotates relative to the housing 102 to open and close an intake passage 104 in the housing 102.
The internal combustion engine is provided with a cylinder head 106 coupled to the housing 102, and a cylinder block 107 having a cylinder bore formed therein. The cylinder head 106 includes an electromagnetic fuel injection valve 111, (i.e., injector) that injects fuel, an intake valve 113 that opens and closes an intake port 112, and an exhaust valve 115 that opens and closes an exhaust port 114. The cylinder bore of the cylinder block 107 receives a piston 116 sliding therein.
As shown in FIG. 8A, the control valve 105 is generally flat and includes a pair of partitions 121 formed at two ends of the upper end thereof. A main aperture 122 is defined between the partitions 121 to allow the passage of the intake air when the intake flow control valve 105 is placed in the fully closed position (shown in solid lines in FIG. 8B). Also, four sub-apertures 123 are included in the control valve 105 at the edges thereof and adjacent the valve shaft 103. The sub-apertures 123 each have a smaller area than the main aperture 122.
The main aperture 122 can cause occurrence of a liquid pool of fuel (i.e., residual gasoline) near the intake flow control valve 105 as shown in FIG. 7. If the fuel in the liquid pool flows into the combustion chamber 101 (e.g., when the vehicle is on an incline), combustion can be incomplete and the engine can malfunction.
In partial response to this problem, for the intake vortex generator disclosed in JP-A-2003-293775, when the internal combustion engine is cooled and the amount of intake air flow is small, the intake flow control valve 105 is placed in the fully closed position such that a tumble flow is created in the combustion chamber 101. Thereupon, in addition to the main intake flow passing through the main aperture 122, intake sub-flows occur through the sub-apertures 123 of the intake flow control valve 105 so as to counter a return flow of a portion of the main intake flow. Thus, it is less likely that the liquid pool will collect near the intake flow control valve 105.
Typically, at the starting of the internal combustion engine, during idling, and/or at low engine speeds the intake flow control valve 105 is fully closed to cause the main, intake flow through the main aperture 122 into the combustion chamber 101, whereby a tumble flow is generated in the combustion chamber 101 to increase the combustion efficiency in the combustion chamber 101 and to improve fuel consumption. Then, during other running conditions of the engine, the intake flow control valve 105 is fully opened (shown in phantom in FIG. 8B) to allow the intake air to flow directly and to stop tumble flow.
In some operating conditions of the engine (e.g., at low engine speeds), the intake flow control valve 105 is positioned in an intermediate position between the fully open and fully closed position. As a result, a tumble flow is generated during an increase in the amount of intake air flowing into the combustion engine 101 to a certain extent. However, when the valve 105 is positioned in the intermediate position, the respective axes of the sub-apertures 123 are not aligned with the flow direction of the intake air. Accordingly, the flow rate of the sub-intake flowing through the sub-apertures 123 into the intake port 112 is decreased. This causes a reduction in velocity of the sub-intake flow such that return flow of the main intake flow is more likely. As a result, a liquid pool of fuel is more likely to develop near the intake flow control valve 105.
Furthermore, the main aperture 122 and the four sub-apertures 123 are typically formed by cutting operations. Then, the two ends of the valve shaft 103 in the axis direction are rotatably attached to the housing 102. Next, the intake flow control valve 105 is inserted into an inserting hole of the valve shaft 103 so that the intake flow control valve 105 is coupled to the housing 102 and the valve shaft 103. This manufacturing process can be time consuming and relatively expensive.
Moreover, when the intake flow control valve 105 is in the fully closed position, the valve 105 can experience an impact load during operation (e.g., from excessive pressure such as depression at the engine manifold or from an irregular pressure incidental to abnormal combustion such as in a back fire). As such, stress can concentrate adjacent the main aperture 122 and the four sub-apertures 123, thus decreasing the operating life of the intake flow control valve 105. In partial response to this problem, the intake flow control valve 105 can be increased in thickness to improve the strength thereof. However, this causes an increase in size and weight of the intake vortex generator. Also, to improve the strength of the valve 105, the valve 105 can be made of high-strength material. However, this further increases the cost of the intake flow control valve 105.